Inspecting molecular aggregate quadratic vibronic coupling effects using squeezed coherent states
We present a systematic comparison of three quantum mechanical approaches describing excitation dynamics in molecular complexes using the time-dependent variational principle (TDVP) with increasing sophistication trial wavefunctions (ansatze): Davydov D 2 , squeezed D 2 (sqD 2 ) and a numerically ex...
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Published in | Physical chemistry chemical physics : PCCP Vol. 25; no. 3; pp. 175 - 1716 |
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Main Authors | , , |
Format | Journal Article |
Language | English |
Published |
England
Royal Society of Chemistry
18.01.2023
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Subjects | |
Online Access | Get full text |
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Summary: | We present a systematic comparison of three quantum mechanical approaches describing excitation dynamics in molecular complexes using the time-dependent variational principle (TDVP) with increasing sophistication trial wavefunctions (ansatze): Davydov D
2
, squeezed D
2
(sqD
2
) and a numerically exact multiple D
2
(mD
2
) ansatz in order to characterize validity of the sqD
2
ansatz. Numerical simulations of molecular aggregate absorption and fluorescence spectra with intra- and intermolecular vibrational modes, including quadratic electronic-vibrational (vibronic) coupling term, which is due to vibrational frequency shift upon pigment excitation are presented. Simulated absorption and fluorescence spectra of a J type molecular dimer with high frequency intramolecular vibrational modes obtained with D
2
and sqD
2
ansatze match the spectra of mD
2
ansatz only in the single pigment model without quadratic vibronic coupling. In general, the use of mD
2
ansatz is required to model an accurate dimer and larger aggregate's spectra. For a J dimer aggregate coupled to a low frequency intermolecular phonon bath, absorption and fluorescence spectra are qualitatively similar using all three ansatze. The quadratic vibronic coupling term in both absorption and fluorescence spectra manifests itself as a lineshape peak amplitude redistribution, static frequency shift and an additional shift, which is temperature dependent. Overall the squeezed D
2
model does not result in a considerable improvement of the simulation results compared to the simplest Davydov D
2
approach.
We present a systematic comparison of three quantum mechanical approaches describing excitation dynamics in molecular complexes using the TDVP with increasing sophistication trial wavefunctions to characterize the validity of the sqD
2
ansatz. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 1463-9076 1463-9084 |
DOI: | 10.1039/d2cp04212f |